Dynamic decoupler for improved attitude control

Abstract

The invention provides a method for controlling the precession of a spinning spacecraft (20) which allows the spacecraft body to respond to an input torque without the nutation normally attendant when an input torque is applied about one transverse axis to accelerate a spinning spacecraft about that one axis. Dynamic decoupling eliminates nutation through the impression of additional derived feedback torques (44,46) to the input torque control of a spinning spacecraft to oppose or cancel the intrinsic cross-coupling terms (34,36) of the spinning spacecraft's gyrodynamics that give rise to the nutation. Thus, a single spacecraft design can provide the benefits of a spinning bus such as a simplified thruster control system for orbit control, improved temperature environment for many payload elements, spin-averaging of body-fixed disturbances and gyro drift errors, and propellant management as well as the major benefit of a body-stabilized or non-rotation spacecraft design which is freedom from nutation and hence improved performance.

What is claimed is: 
     
       1. A method for reducing nutation induced during precession about a single axis of a spinning spacecraft having a gyro-based attitude control system, the method comprising: generating compensated control moment command signals which compensate for reactant cross-coupling torque produced about transverse axes by said gyro in reaction to an original control moment command signal by adding a rate gyro derived feedback term in opposition to the reactant cross coupling torque;   communicating said compensated control moment command signals to said spacecraft; and   applying said compensated control moment command signals to said spacecraft.   
     
     
       2. A method for reducing nutation induced by precession about a single axis of a spinning spacecraft having a gyro-based attitude control system, the method comprising: generating compensated control moment command signals compensated for reactant cross-coupling torque by including a rate gyro derived feedback term in opposition to the reactant cross-coupling torque;   communicating said compensated control moment command signals to said spacecraft;   applying said compensated control moment command signals to said spacecraft;   determining amount of cross-coupling effect produced about said transverse axes by said gyro in reaction to said original control moment command signal;   separating said original control moment command signal into x and y components;   modifying said x and y components to compensate for said reactant cross-coupling torque; and   converting said modified x and y component signals to control torque to form said compensated control moment command signals.   
     
     
       3. The method of claim 2, wherein said modifying is carried out using ring laser gyroscopes. 
     
     
       4. The method of claim 2, wherein said modifying is carried out using dynamically-tuned gyroscopes. 
     
     
       5. The method of claim 2, wherein said modifying is carried out using fiber gyroscopes. 
     
     
       6. The method of claim 2, wherein said modifying is carried out using hemispherical resonant gyroscopes. 
     
     
       7. The method of claim 2, wherein said modifying is carried out using electrostatically suspended gyroscopes. 
     
     
       8. The method of claim 2, wherein said converting is carried out using magnetic actuators. 
     
     
       9. The method of claim 2, wherein said converting is carried out using electromagnetic actuators. 
     
     
       10. The method of claim 2, wherein said converting is carried out using thrusters. 
     
     
       11. The method of claim 2, wherein the step of generating is performed on the ground. 
     
     
       12. The method of claim 2, wherein the step of generating is performed on board said spinning spacecraft.